Laboratory studies of isotope exchange in ion-neutral reactions: interstellar implications

1981 ◽  
Vol 303 (1480) ◽  
pp. 535-542 ◽  
Keyword(s):  
Low Temperatures ◽  
Isotope Exchange ◽  
Laboratory Data ◽  
Isotopic Ratios ◽  
Laboratory Studies ◽  
Terrestrial Environment ◽  
Interstellar Clouds ◽  
Ion Molecule Reactions ◽  
Significant Process ◽  
Molecule Interactions

The rare stable isotopes of several elements (e.g. D, 13 C and 15 N) have been detected in several interstellar molecules, and their abundance relative to the more common isotope is often enhanced above that in the solar-terrestrial environment. Important questions to answer are to what extent the isotopic ratios in the molecules are representative of those in the cloud matter as a whole, and whether fractionation of the heavier isotope into the molecules via ion—molecule interactions is a significant process. A laboratory study of isotope exchange in ion-molecule reactions has therefore been carried out, the results of which indicate that fractionation of heavy isotopes can occur very efficiently at low temperatures. Consideration is given in this paper to reactions in which H-D, 12 C - 13 C, 14 N - 15 N and 16 O - 18 O exchange occurs, and it is shown how better estimates of the electron density and the temperature in interstellar clouds have been obtained from these laboratory data.

scholarly journals Gas Phase Synthesis of Amino-, Cyano- and Nitroso-Compounds in Interstellar Clouds

1980 ◽  
Vol 87 ◽  
pp. 311-315
Author(s):  
Nigel G. Adams ◽  
David Smith
Keyword(s):  
Gas Phase ◽  
Laboratory Data ◽  
Nitroso Compounds ◽  
Phase Synthesis ◽  
Interstellar Clouds ◽  
Gas Phase Synthesis ◽  
Ion Molecule Reactions

From our laboratory data relating to several hundreds of ion-atom and ion-molecule reactions at thermal energies, we qualitatively describe probable chemical paths to the synthesis of amino-, cyano-and nitroso-compounds in interstellar clouds.

scholarly journals Interstellar Molecules in Meteorites

1989 ◽  
Vol 135 ◽  
pp. 383-388
Author(s):  
J. F. Kerridge
Keyword(s):  
Solar System ◽  
Interstellar Medium ◽  
Low Temperatures ◽  
Isotopic Fractionation ◽  
Early Solar System ◽  
Interstellar Molecules ◽  
Interstellar Clouds ◽  
Ion Molecule Reactions ◽  
Chondritic Meteorites ◽  
Interstellar Material

Substantial enrichment of deuterium, D, in certain components of chondritic meteorites is interpreted as a record of isotopic fractionation during ion-molecule reactions at the very low temperatures characteristic of dense interstellar clouds. Whether those meteorites still contain the actual molecules that were synthesised in the presolar interstellar medium, or whether the interstellar material was recycled into a later generation of molecules within the early solar system is not known.

Porcellio spinicornis Say (Isopoda) demography. II. A comparison between field and laboratory data

1976 ◽  
Vol 54 (6) ◽  
pp. 825-842 ◽  
Author(s):  
Donald J. McQueen
Keyword(s):  
Field Data ◽  
Laboratory Data ◽  
Field Population ◽  
Laboratory Studies ◽  
The Third ◽  
Terrestrial Isopod ◽  
Independent Laboratory ◽  
Demographic Study ◽  
June July ◽  
Rates Of Growth

Field data from a demographic study of the terrestrial isopod Porcellio spinicornis Say were analyzed and compared with laboratory data reported by McQueen and Carnio. On the study area, which covered 482.8 m2, it was observed that reproduction began when average temperatures were > 13 °C, and that about 86% of the individuals produced one brood and about 30% produced two broods. During 1972, 25 654 offspring were produced and during 1973, 27 664 offspring resulted from reproduction, which took place during May, June, July, and August. By October of both years, these animals attained sizes ranging from 10 to 30 mg and exhibited 42 to 47% survivorship. During the next summer, females grew to between 30 and 50 mg and males to between 20 and 40 mg, and survivorship ranged from 15% in May to 2% in August. During the third summer, females attained sizes ranging from 80 to 100 mg and males from 40 to 70 mg. Survivorship during this period ranged from 1% in May to 0% in August. All rates of growth, reproduction, and survival, as well as reproductive periodicity, agreed with independent laboratory studies conducted under controlled conditions. During the 3 years studied the field population remained relatively constant and appeared to be limited by temperature conditions.

scholarly journals COMPOSITION, MICROSTRUCTURE AND PROPERTIES OF QUATERNARY CLAYS OF THE PRIKHANKAYSKAYA DEPRESSION (PRIMORYE)

2019 ◽  
Vol 14 (1) ◽  
pp. 20-34
Author(s):  
T. G. RYASHCHENKO ◽  
N. N. UKHOVA ◽  
S. I. SHTELMAKH ◽  
N. I. BELYANINA ◽  
P. S. BELYANIN
Keyword(s):  
Clay Minerals ◽  
Laboratory Data ◽  
Chemical Properties ◽  
Exchange Capacity ◽  
Climatic Conditions ◽  
Water Soluble ◽  
Laboratory Studies ◽  
Microstructural Parameters ◽  
Physical Chemical ◽  
Study Results

The article considers the study results of composition, microstructure and physical-chemical properties of the quaternary clays of the Prikhankayskaya depression in district of the lake Khanka (Primorye) on the example of air-dry samples of geological borehole 45-b in the range of 18–62 m. The objective of research was to obtain new information about the properties of widespread clay sediments in this area using geologic-lithological materials and laboratory data. The schematic geologic-lithological column was composed with the selection of various zones in the quaternary clay sediments section and the border with sediments of the Neogene System. The methodological scheme of laboratory studies of clays was proposed. This scheme includes the determination of chemical and microelement composition, clay minerals, contents of carbonates, water-soluble salts, mobile forms of aluminum oxide, humus, as well as microstructural parameters (method «Microstructure») and some physical-chemical properties. Geochemical coefficients (Kz, CIA, CIW, ICV) determined the degree of chemical maturity of clays and confirmed the results of palynological studies reflecting the fluctuations of the climatic conditions of their formation. For the group of toxic microelements for the first time the special indicator (Zc) was calculated. Which was the criterion for a degree of pollution of the clay sediments section. Clay minerals of the quaternary clays are represented by smectite and hydromica. The clear change in the mineral association was found when passing to the Neogene sediments (kaolinite prevails). The method «Microstructure» revealed the aggregated type of clays microstructure, the domination of the particles of coarse dust fraction among the primary (free) particles and the almost complete absence of the particles of fine-grained sand fraction, the participation of various fractions in the composition of aggregates. The variants of the formation of certain types of aggregates (on sizes) in the fluviolacustrine «khankayskiy» clays are presented. Solid part density, water resistance (soaking time), sedimentation volume, plasticity, relative swelling (samples-pastes) were determined using standard methods for clays. By special methods, the cation exchange capacity was measured and the calculated values of the plasticity index were obtained from forecasting formulas using the yield limit. The proposed methodological scheme of complex laboratory studies of clay sediments can be recommended for problematic geologic-lithological and engineering-geological sections.

Rates and potential mechanism of anaerobic nitrate-dependent microbial pyrite oxidation

2012 ◽  
Vol 40 (6) ◽  
pp. 1280-1283 ◽  
Author(s):  
Julian Bosch ◽  
Rainer U. Meckenstock
Keyword(s):  
Electron Acceptor ◽  
Pyrite Oxidation ◽  
Laboratory Data ◽  
Laboratory Studies ◽  
Mineral Phase ◽  
Terminal Electron Acceptor ◽  
Micro Organisms ◽  
Open Question ◽  
Sulfur Containing ◽  
Positive Results

Pyrite (FeS2) is a major iron- and sulfur-containing mineral phase in the environment. Oxidation of pyrite by aerobic micro-organisms has been well investigated. However, the reactivity of pyrite under anoxic conditions is still an open question. In the present paper, we summarize field and laboratory data on this chemolithotrophic respiration process with nitrate as terminal electron acceptor. Geochemical and stable isotope field data indicate that this process is occurring. Laboratory studies are more ambiguous, but recent positive results provide evidence that anaerobic microbial pyrite oxidation can, in fact, occur with nitrate as electron acceptor.

Laboratory Studies of Cirrus Cloud Processes

Cirrus ◽  
2002 ◽  
Author(s):  
Paul DeMott
Keyword(s):  
Laboratory Data ◽  
Ice Formation ◽  
Formation Mechanisms ◽  
Laboratory Studies ◽  
Theoretical Concepts ◽  
Upper Troposphere ◽  
Microphysical Properties ◽  
Nucleation Mechanisms ◽  
Remote Measurements ◽  
Many Sources

A number of processes that play a role in the formation, evolution of microphysical properties, and radiative characteristics of cirrus clouds are amenable to investigation in a laboratory setting. These laboratory studies provide fundamental data for quantifying and validating theoretical concepts and help guide investigations involving direct and remote measurements of cirrus. Laboratory data also may be used for formulating parameterizations for numerical cloud models, especially where information is incomplete or full descriptions are not possible. This chapter reviews results from laboratory studies of ice formation, ice crystal growth, radiative transfer, and aerosol scavenging and transformation in the cirrus environment. Emphasis is placed on ice formation in cirrus conditions. The related topic of contrail formation is covered separately in this book. The formation mechanisms of lower stratospheric clouds are reviewed elsewhere (e.g., Tolbert 1994; Peter 1996; Carslaw et al. 1997; Koop et al. 1997a). Laboratory studies of cirrus ice formation are at a rapidly developing stage, so it is useful to provide significant background bases for current and needed studies. Key issues are aerosol composition, ice nucleation mechanisms, and the synergy between theory and laboratory measurements. Vali (1996), Baker (1997) and Martin (2000) discuss some of these issues in review papers. Upper tropospheric aerosol particles play an important catalytic role in the formation of cirrus. The nucleation process is important in determining the microphysical properties of cirrus. Numerical modeling studies (e.g., Jensen and Toon 1994; DeMott et al. 1994, 1997; Heymsfield and Sabin 1989) indicate that variation in the factors that drive the nucleation of ice and variations in the physical and chemical characteristics of aerosol particle populations lead to the formation of cirrus with different microphysical characteristics. Knowledge of the physics and chemistry of aerosols in the upper troposphere and lower stratosphere has evolved at a rapid pace. A detailed accounting of this topic is beyond the scope of this chapter. For the purpose of the present discussion, it is sufficient to note that the aerosol from which cirrus nucleate may vary significantly from place to place. Differences in aerosol properties in time and space occur because particles can arrive to the upper troposphere in so many ways and from so many sources.

Sign in / Sign up

Export Citation Format

Share Document